The tendency of a solid or liquid elements in a plastic or composite material (such as particle board) to vaporize over time. Outgassing can occur in some plastics and paints if they have not finished drying,resulting in adhesive failure to anything applied over them. Outgassing also describes the release of impurities in vacuum systems such as neon tubes during processing.

The characteristic of a solid or liquid to vaporize under heat and migrate to the surface of the material that it is in. Outgassing can occur in some plastics and paints if they are not thoroughly dried, resulting in adhesive failure to anything applied over them. Outgassing is also common in plastics that have been molded because to the process of molding often traps gasses and moisture.